A contraceptive method could almost halve the risk of cervical cancer according to a one of the largest studies of its kind.

The report, published Tuesday by the Lancet Oncology, found that out of 20,000 women, those with a history of using this Intra-Uterine Devicse (IUDs), had half the risk of developing cervical cancer compared with women who had never one.

IUDs are T-shaped objects that sit inside the womb, and protect against pregnancy either by releasing hormones or by using copper to reduce the mobility of the sperm and preventing it from joining with an egg. Additionally the foreign body inside the uterus irritates the lining and wall making it hard for an embryo to implant.

Cervical cancer is primarily caused by the human papillomavirus infection (HPV). Although the virus is not prevented through IUD use, the contraceptive could prevent HPV from developing into cervical cancer, researchers said.

Authors say this could be because precancerous cells are destroyed as the device is inserted, and IUDs might provoke a long lasting immune response, reducing the likelihood of HPV progression.

The authors say: “The associations found in our study strongly suggest that IUD use does not modify the likelihood of prevalent HPV infection [the cause of cervical cancer], but might affect the likelihood of HPV progression to cervical cancer ... this effect does not seem to be due to differences in screening histories between users and non-users.”

The length of IUD use did not significantly alter cervical cancer risk, according to the study.

The risk was reduced by nearly half in the first year of use and the protective effect remained significant even after 10 years of use.

IUDs are available free on the NHS or cost between £150-£250 to have inserted privately. HPV vaccinations cost £600, although the NHS has started a national programme to vaccinate girls from 12-17. Regular screening through smear tests is also an accepted method of countering the risk of cervical cancer.

Dr Karl Ulrich Petry from the Klinikum Wolfsburg, Wolfsburg, Germany says of the study: “[These] surprising results should spark new research and might lead to revision of our current understanding of the genesis of cervical cancer.”

The study was carried out by Xavier Castellsagué from the Cancer Epidemiological Research Program, Institut Català d’Oncologia, L’Hospitalet de Llobregat, Catalonia, Spain and colleagues.